Influence of operating parameters on slurry erosion of stainless steel f6nm

Abstract

This work is an investigation on slurry erosive wear resistance of stainless steel F6NM used as hydro-turbine material in Dul-Hasti power plant using erodents collected from the same hydro power station dam site located in Kashmir, India. Erodents used in slurry mixture were segregated into three sizes 125, 225 and 325 µm. The minerals found in erodent were quartz, feldspar, biotite, hornblende and garnet with quartz as the major constituent. The effect of five operating parameters namely (A) sediment concentration (20-30 wt.%), (B) particle size (125-325 µm), (C) angle of impact (15-45 degree), (D) test duration (450-750 min.) and (E) rotational speed of slurry (500-1000 rpm) on erosive wear of F6NM steel were studied using slurry erosive wear tester (TR-40) at room temperature. The experimental runs were carried out by adopting response surface methodology (RSM) with face centered design for adequate number of runs. It was perceived that three parameters namely rotational speed of slurry, sediment particle size and sediment concentration have major impact on erosive wear. The contribution of rotational speed of slurry, particle size and sediment concentration is 30.58 %, 18.82 % and 17.64 % respectively for an overall erosion wear. It was observed that increased sediment concentration, higher values of sediment particle size, increasing angle of impact (up to 30 degree only), increased test duration and higher rotational speed of slurry resulted in higher erosive wear material loss. Post mortem studies of the eroded samples (surfaces) were carried out by scanning electron microscopy (SEM) to reveal probable mechanism of material removal. The SEM images of worn surfaces reveal the material is mainly removed owing to formation of abrasive wear tracks, raised lips, crater and grooves due to ploughing and cutting action of erodent particles. Further SEM micrographs of erodent particles (particularly at high speeds and long durations) have been rendered blunt with total or partial removal of sharp edges and thus making them ineffective for further participation on erosive wear process.